In a solar power generation module (hereinafter, sometimes referred to simply as “module”) that converts solar light energy into electricity, a connection structure, such as a junction box or a connector, is provided in each module for connecting a cable between modules in order to extract the electricity in a useful form. A bypass diode, for example, is arranged in the junction box, so that even if the output of a module has decreased because the surface of a solar power generation module is partially in shadow, or a battery cell is broken, the effect of such a problem can be minimized. In this case, since the bypass diode generates heat, the whole junction box needs to be heat resistant. Proposed countermeasures against this heat generation have included increasing the number of diodes, attaching a metal heat sink in order to conduct the heat away, and dissipating the heat by increasing the volume of the junction box (e.g., refer to Patent Documents 1 and 2).
As the material forming the connection structure, such as a junction box and a connector, a thermoplastic resin may be used, for example.
Since solar power generation modules are often placed outside, the thermoplastic resin forming the connection structure, such as a junction box and a connector, not only needs to have the performance that is conventionally required for electrical and electronic component applications, such as electrical insulating properties typified by anti-tracking performance, and excellent flame retardancy, mechanical properties, impact properties, water resistance, chemical resistance, and dimensional stability, but to also have impact strength at low temperatures.
Further, since the length of service of solar power generation modules is increasing, it is now important for the thermoplastic resin forming the connection structure, such as a junction box and a connector, to have thermal aging resistance properties (properties that maintain performance when exposed for a long duration to a high-temperature usage environment). In addition, the connection structure, such as a junction box and a connector, needs to have a good design and to be space saving.
In response to such needs, a connection structure for a solar power generation module has been proposed that has excellent impact properties at low temperature and long-term heat resistance even when being made thinner and more compact (e.g., refer to Patent Document 3).